1. Field of Use
This invention relates generally to apparatus for supplying and installing plastic expansion rivets in a hole in a workpiece. In particular, it relates to an improved expansion rivet installation tool for such apparatus and to improved means for operating such tool.
2. Description of the Prior Art
A typical expansion rivet comprises a hollow expandable rivet body and a mandrel or pin disposed in a bore in the rivet body. Such an expansion rivet is used, for example, to secure two flat panels together. In use, the unexpanded rivet body is inserted into aligned holes in the panels until a flange or head on the rivet body engages the outside of one panel. The flange is then held stationary against the panel while the mandrel is pulled axially to effect expansion of the rivet body shank on the outside of the other panel, whereby the panels are trapped between the rivet body flange and the expanded rivet body shank. Thereafter, if the mandrel has a breakaway portion, additional axial pulling force is exerted on the mandrel to cause that portion of the mandrel projecting from the rivet body to break away, whereupon the broken-away portion is discarded. Heretofore, hand-held manually operable tools of various types were employed to install expansion rivets having breakaway mandrels. Such tools required the user to install each expansion rivet in the tool, to manipulate the tool so as to insert the rivet body into the aligned holes in the panels to be joined, and to manually squeeze components of the tool to effect axial motion of the mandrel, expansion of the rivet body and breakaway of the projecting mandrel portion. This approach was time-consuming, tedious, costly and fatiguing for the tool-user who furnished manual power to operate the tool. Furthermore, broken-away mandrel portions in the form of small cylinders were usually discarded on the floor of the workplace and posed a risk that the tool-user or other persons might slip and fall. It is desirable, therefore, to provide improved apparatus and tools for supplying and installing expansion rivets.
U.S. Pat. No. 4,671,143 discloses an automatic screw feeding machine having driver jaws for a driver head. The jaws receive conventional slotted screws, one at a time, from a source and have a pair of oppositely disposed separable elongated cantilever springs which bias outwardly to receive and hold the screw. A reciprocably movable and rotatable screwdriver tip advances through a bore in the driver head, engages the slot in the screw head and rotates the screw into a threaded hole in a workpiece, whereupon the cantilever springs release the screw and reclose and the screwdriver tip retracts. However, this prior art automatic screw feeding machine is not usable to install expansion rivets.